Courage almost upset feline (6)
I believe the answer is:
cougar
'feline' is the definition.
(cougar is a kind of feline)
'courage almost upset' is the wordplay.
'almost' means to remove the last letter (most of the word but not all of it).
'upset' is an anagram indicator.
'courage' with its last letter taken off is 'courag'.
'courag' with letters rearranged gives 'COUGAR'.
(Other definitions for cougar that I've seen before include "Cat, aka puma" , "Another name for puma" , "N American mountain lion, puma" , "American wildcat, puma" , "Big cat" .)